1. Technical Field
The present invention relates to an improved method for the production of reduced oil potato chips and more particularly to a method of controlling the oil-pickup within the fryer.
2. Description of Related Art
Commercial production of potato chips typically involves a continuous process wherein sliced potatoes are continuously introduced into a vat of frying oil at a temperature of about 365° F. (about 185° C.) or higher, conveyed through the oil by paddles or other means, and removed from the oil after about two and one-half to three minutes of frying by an endless conveyor belt when the moisture content of the chips has been reduced to about 2% by weight or less. The resulting product generally has texture and flavor characteristics which are usually recognizable by consumers as typical commercially produced continuous process potato chips.
Potato chips produced by batch processes in kettle fryers have texture and flavor characteristics which are usually recognized by consumers as being distinctly different from typical commercially produced continuous process potato chips. As the name implies, batch process kettle frying of potato chips involves placing a batch of potato slices in a kettle of hot oil, e.g., at a temperature of about 300° F. (about 150° C.). In the conventional kettle fryers used in the production of kettle-style chips, the cooking oil temperature follows a generally U-shaped time vs. temperature profile as illustrated in FIG. 5 of U.S. Pat. No. 5,643,626, assigned to the same assignee as the present invention, which is hereby incorporated by reference. Upon introduction of the potato slices into the oil, the temperature of the oil typically drops quite rapidly by as much as 50° F. (about 28° C.) or more. As depicted by the Figure, the oil temperature falls to a low point temperature of about 240° F. (116° C.) for a low point time of about 4 minutes. Heat to the kettle is then quickly increased and then the temperature of the oil begins to gradually rise, reaching about the initial frying temperature of about 300° F. (roughly 149-150° C.). The resultant potato chip has a moisture content of between 1.5% to 1.8% by weight. However, unlike Henson '626, which deals only with batch-fry applications, the present invention uses certain findings regarding frying temperature profiles to provide a method for actually controlling the amount of oil uptake in the fried product.
Batch fried chips are generally harder and crunchier than continuously fried chips and have a flavor that some consumers find more appealing than typical continuously fried commercial chips. It is believed in the art that the U-shaped temperature-time profile imparts the intense flavor and unique mouth feel characteristic of kettle-style chips. The commercially available kettle fryers, however, are relatively unsophisticated pieces of equipment that are significantly constrained by burner capacity and heat transfer capacity. Thus, the observed U-shaped temperature-time profile is unavoidable with the conventional kettle equipment, as the system cannot supply heat quickly enough to overcome the large heat sink created by the addition of a batch of raw potato slices. Changes in oil volume, initial fry temperature or potato batch weight will cause changes in temperature profile and finished product attributes. Therefore, the production of potato chips having the desired kettle-style attributes requires the adjustment of the process parameters in a manner that results in the U-shaped temperature-time profile.
Production rates using batch kettle fryers are dependent upon the equipment used. The modern kettles that are utilized in batch processes are generally manufactured of stainless steel, and vary in size and capacity. The kettles typically are heated by gas burners positioned directly under the kettle floor. Fryer capacities range from as few as 60 pounds per hour to up to 500 pounds per hour (finished product basis), although most batch fry operations have kettle fryers that can manufacture between 125 and 200 pounds of chips per hour. In order to efficiently use a batch kettle fryer of a given size, it is necessary to maintain a particular “load” or amount of potato slices per volume of oil, in order to achieve the desired frying temperatures. These and other constraints provide limits on the amount of throughput using batch kettle fryers. By contrast, potato chips made by a continuous process can employ continuous fryers capable of producing 1,000 to 5,000 pounds per hour of finished product. The kettle or batch process is therefore less economical than a continuous process.
In manufacturing kettle-style chips, some of the distinctive flavor and texture is believed to be attributable to the use of unwashed slices (as opposed to washed slices.) When washed, some of the surface starch and other matter that may contribute to flavor is removed. However, the slices are usually asitated during frying to prevent stickiness due to the presence of surface starch. It would therefore be desirable to help reduce stickiness while also retaining the surface starches believed to contribute to kettle-style texture and taste.
One very important product variable is die oil content. While low oil content is desirable for nutritional reasons, excessively low oil content levels result in poor taste and texture. Low oil content is desirable for yet another reason: marketing. The trend in the snack food industry has been to provide consumers with healthier options of food snacks. Many consumers prefer healthier alternatives to the traditional snack foods. As a result, there is great demand for healthier snack foods. One option of making the traditional potato chip healthier is by decreasing the oil content of the chip.
Traditional potato chips made by continuous-frying processes typically have oil contents ranging from about 34-38% oil by weight. The traditional batch-fried kettle chip has an oil content of about 30% oil. Interestingly, it was discovered that kettle-style potato chips produced from a continuous process (also known as “continuous-fried kettle chips,” “continuous-kettle-fry chips” or “CKF chips”) exhibit lower oil content ranges of about 20% to about 23% by weight (20060019007, page 15). Other differences between traditional (or regular) potato chips, batch-fried kettle chips, and continuous-fried kettle chips, include: differing rates of cooking; differing rates of heating; and differing rates of moisture evolution. For example: whereas regular potato chips are usually fried for 2-to-3 minutes at roughly 365° F. (about 185° C.) or higher, batch-fried kettle-style potato chips are typically fried for about 7-to-9 minutes within a temperature range of about 230° F. (roughly 110° C.) to a temperature no greater than about 400° F. (roughly 200° C.).
There are several known methods for reducing oil content. For example, U.S. Pat. No. 4,917,919 discloses a method of coating a potato with aqueous polyvinylpyrrolidone. However, the coated chip exhibits a moisture content of about 4% by weight, which greatly compromises shelf stability.
U.S. Pat. No. 4,537,786, also assigned to the same Assignee of the present invention, teaches using thicker potato slices to reduce oil content. It further teaches subjecting the fried chip to a stream of hot air which removes excess oil. Unfortunately, the hot air accelerates the oxidation of the oil and reduces shelf life.
Finally, U.S. Pat. No. 4,721,625 discloses subjecting the fried chip to saturated steam. However, like U.S. Pat. No. 4,917,919, this method results in increased moisture content and could require costly subsequent drying.
Thus, while some pre-treatment and post-treatment methods are known in the art, they are all limited in ability and have significant drawbacks. Additionally, there are virtually no methods known to reduce oil pick-up within the fryer. Consequently, a need exists that reduces oil take-up of potato chips while in the fryer.